Most owls are active year-round and most species eat every day. Owls have a low percentage of body fat during the warm months of the year. However, during the cold months, the percentage of body fat does increase in some owl species such as the Snowy Owl. These fat reserves provide energy when food is scarce.

Owl metabolism

The rate of metabolism (turning food into energy) in owls is generally quite high. As a result, owls must eat frequently, which also means that they must hunt frequently. Small owls, such as the Elf Owl, have extremely high metabolisms that require them to consume enough prey to equal 50% of their body weight every day. Larger owls have slower metabolisms and eat less than smaller owls do in proportion to their body weight. The Snowy Owl has a metabolism which at times greatly differs from that of all other owls. It might fast for over a month during winter due to the scarcity of prey. During the fasting period, the Snowy Owl relies heavily on its fat reserves to keep it going.

Owls, like most birds, cannot chew their food and usually eat their prey whole, most of the time not separating edible parts of the prey from the inedible ones. However, when they have caught something that is too big to swallow whole, they will pick the animal apart before consuming it. Large owls, such as the Great Horned Owl, commonly attack prey near their own size or even larger. Examples include foxes, skunks, weasels, and even smaller owls. The tiny Pygmy Owl has been known to attack and kill quail, which are twice its weight.

Certain types of prey might not be available to owls at different times of the year due to hibernation, migration, or other reasons. Because of this, most owls are opportunistic hunters, eating anything available in times of need. However, many owl species do prefer rodents. Barn Owls in particular will pass up an easy kill to dine on their preferred rodent delicacy.

Most of the time older owlets are friendly to their younger siblings. They may help feed the younger chicks and help them keep warm. However, owlets sometimes cannibalize their younger or weaker siblings if food is scarce. This often occurs when there is a wide gap between the ages of the oldest and youngest chicks in a nest.

Here is a partial list of owl prey. Bear in mind that larger species of owls generally eat larger prey (like squirrels) and smaller species of owls generally eat smaller prey (like insects).